Zeckendorf Development is a privately owned real estate development firm headed by the multi-generational Zeckendorf family, which became known for selling the United Nations its 17-acre East Side location. Today, the firm has sold nearly $4 billion in high-end housing. The firm has a number of highly successful properties under its belt, including 515 Park Avenue and 15 Central Park West, the latter of which set record apartment prices in 2007. More recently, Zeckendorf developed a formerly vacant lot in the Turtle Bay neighborhood and created the 43-story 50 United Nations Plaza. Zeckendorf partnered with Global Holdings (with which Zeckendorf also collaborated on 15 Central Park West). The luxury apartment building was initially seen as less successful than other Zeckendorf properties, as many of the buildings units sold for less than asking price in 2015. The firm has said it is okay with the slow but steady rollout of units in the building as long as higher prices are achieved.